Heated towel rails and the electrocorrosion that forms on them

It all starts with small spots and ends with pipe failure

Electrocorrosion of pipelines is a rather unpleasant phenomenon. And it’s not just about the appearance of the pipes: the development of corrosion processes gradually leads to a violation of the integrity of the walls and connections. So over time, both the reliability of the pipeline and its service life will decrease.

To understand how to deal with this phenomenon, you need to understand its nature. That is why it is necessary to understand the most important practical aspects of electrical corrosion of plumbing pipes. This is what we will do.

Do I need to ground a heated towel rail?

First you need to know that grounding (constructing grounding loops with your own hands) is not required if:

1. 1. You are using an electric heated towel rail (such heated towel rails are usually equipped with special plugs that contain a grounding wire, all this is connected to an outlet, and the outlets themselves must already be connected to the ground loop).
2. 2. You live in a private house or apartment, and you have a separate heating system.

The heated towel rail must be grounded in the following cases:

1. 1. If your dryer is connected to the heating system with a metal-plastic pipe. Inside the metal-plastic pipe there is aluminum, which conducts electric current: at the joints where the fittings are located, the electrical circuit is broken. Accordingly, such a heated towel rail must be connected to a ground loop or to a hot water supply riser.
2. 2. If your hot water supply system is made of metal-plastic pipes.

How to ground a heated towel rail

All electric heated towel rails, as mentioned above, are connected to a grounded socket, and such dryers have a grounding wire with a separate contact on the plug. Since heated towel rails are usually installed in the bathroom, you should inspect the outlet to which it will be connected. Such an outlet must be in a special protective casing that prevents moisture from getting inside the outlet itself.

There are 2 main ways to ground a heated towel rail:

1. 1. Using a potential equalization system, which must be installed manually, then ground this system to the general grounding of the electrical panel. This should be done if in a house or apartment, instead of metal communications, communications made of polymers (metal-plastic pipes) are used.
2. 2. Grounding directly the pipe of the heated towel rail body with a regular wire to the steel riser.

To implement grounding of the heated towel rail in the second way, you first need to acquire a clamp, having first removed all the insulating materials from it. This clamp must have a terminal for connecting the wire. Then the clamp is attached to the pipe of the heated towel rail body.

An ordinary copper wire is taken, which should have a cross-section of 4 mm2. This wire on one side is connected to the clamp terminal, the other end must be connected either to the ground of the electrical panel or to a steel riser. In addition, do not forget to connect other devices located in your bathroom to the ground loop.

Friends, also watch the video why you need to ground a heated towel rail.

Similar materials on the site:

• About grounding in simple words
• Why is a bathtub grounded?
• Grounding device design

Creation of a grounding system

It is necessary to create a strong metal connection between the riser pipes and the heated towel rail. Even a novice master can ground it. The ease of operation is explained by the design of towel dryers, which were originally designed for connection to a grounded outlet. If the socket is installed in the bathroom, you will need a special waterproof housing.

The work is performed in the following order:

1. Determine the reliability of the connection between the dryer and the water supply.
2. Check what material the hot water supply pipes are made of. If it is steel, grounding is usually not necessary. In the case of plastic pipes, grounding will be required.
3. Using a steel conductor, connect all metal objects in the room.
4. Make a jumper for grounding. Connect the wire from the switchboard with a jumper.
5. Fix the grounded conductor to the coil. To do this, use a clamp.

This completes the creation of the grounding system. After checking the resistance level, it is ready for use.

Causes of electrocorrosion

The appearance of Foucault eddy currents is a rather complex unpredictable phenomenon. In hot water supply systems, and sometimes in the heating system, such currents appear due to many reasons, seemingly unrelated.

In general, eddy currents are formed when there is a potential difference. When building a house, all metal structures are connected to a common grounding loop, and earlier in construction they used loop grounding, but now they are content with the potential equalization method.

When plastic systems are installed in an apartment instead of an existing metal system, a potential difference arises due to a grounding break (for example, there is one potential on a heated towel rail, and a completely different one on the riser). Hence the potential difference, hence the stray currents. They can also occur as a result of a short circuit or lack of grounding of nearby electrical household appliances, be it a washing machine and so on.

Even the presence/absence of tram tracks in the immediate vicinity plays a role. Stray currents also occur when the insulation of electrical wiring is broken, the network is broken, or grounding is made to the heating system.

All this leads to electrocorrosion of plumbing fixtures, which is also caused by the proximity of two different materials, especially stainless and black steel. The place through which the charge passes into the heated towel rail, as a result, undergoes an electrochemical reaction, so damage occurs there. Such problems are usually solved by directly grounding the heated towel rail itself.

When purchasing a water heated towel rail, you need to familiarize yourself with the rules of its operation, in particular, pay attention to whether the heated towel rail needs to be grounded or not, in order to take this point into account during the repair, and not after the repair is completed

A little about the nature of stray currents and their danger

The reason for the appearance of stray currents acting on your heated towel rail is the difference in potential of grounded structures. And in order to equalize the potentials, it is necessary to create a system in which all metal elements will be in contact with the neutral conductor in the existing input distribution device.

Such a system will ensure maximum safety for the user (if you put your hand on a pipe and grounded equipment, you will not receive a fatal discharge). And this is very important, because the greater the potential difference, the more serious the danger threatens a person. For example:

1. If this value is 4 or 6B, you may receive a 5 mA shock. It will be sensitive but not fatal.
2. If its strength is 50 mA, cardiac fibrillation may develop.
3. And when a human body is exposed to a current of 100 mA, death occurs.

But there are cases where even a small potential difference of 4B became the cause of death.

Why ground a water heated towel rail?

After plastic pipes began to replace ordinary metal pipes, they began to ignore their grounding, mistakenly believing that a metal pipe and a metal-plastic pipe have the same conductivity. This is wrong. There is no contact between the metal-plastic pipe and the aluminum: they are not connected.

Practice shows that 90 percent of heated towel rails begin to leak precisely when metal hot water supply systems are replaced with their plastic counterparts (for example, polypropylene). Old metal pipes are replaced with modern plastic ones in order to reduce eddy currents. However, corrosion continues to manifest itself.

The first symptoms of electrical corrosion are the appearance of rust spots on the heated towel rail, and rust appears even on devices made of stainless steel. In general, all metal electrical products in contact with water are subject to both electrochemical and galvanic corrosion. Electrocorrosion occurs in the presence of stray currents. As a result, the metal is simultaneously exposed to electric current and water, after which metal breakdowns appear, and from there corrosion begins to spread.

When two different metals come into contact, one of which is more chemically active than the other, both metals undergo a chemical reaction. Pure water is a very poor conductor of electric current (dielectric), but due to the high concentration of various impurities, water turns into a kind of electrolyte.

Do not forget that temperature has a great influence on electrical conductivity: the higher the temperature of the water, the better it conducts electric current. This phenomenon is known as “galvanic corrosion”, which is what systematically renders the heated towel rail unusable.

Damage caused by electricity

Main features

A device such as a heated towel rail is often made of stainless steel. This material is highly resistant to rust, which is why the service life of such products is much longer than that of conventional steel heated towel rails.

The first signs are visible on the welds - over time the problem will worsen

But still, sometimes we can observe how pipes that should not rust become unusable. Typically the process develops according to this scenario:

1. First signs. Rust appears on the surface of a stainless pipe in the form of small spots. As a rule, the spots do not exceed the size of a match head and are located in groups.

Processes take place not only outside, but also inside: cross-sectional photo of the threaded part

1. Expansion of the affected area. The rusty spots increase in size and eventually merge into larger spots. At the same time, the intensity of corrosion increases, so that the lesion expands and deepens.

Quite deep defects are already noticeable here

1. Damage to deep layers. If we try to clean off the rust with our own hands, we will see that the metal underneath is destroyed to a sufficient depth. A small funnel is formed under the oxide layer, the walls of which are also subject to corrosion.

The longer you ignore a problem, the more difficult it will be to solve it.

Defects may also appear on fittings

1. Violation of the integrity of the pipe. The process of metal degradation gradually accelerates, which is almost guaranteed to cause serious problems. As a result, either the integrity of the thread of the heated towel rail is compromised, or a hole appears in the pipe under the influence of pressure.

READ MORE: How to connect a pass-through switch: step-by-step instructions

Such processes are typical for pipes made of black and galvanized steel. But if the towel dryer in the bathroom is made of high-quality material (AISI 304/321 steel or analogues), but growths and rust spots still appear on the surface, the problem is electricity.

The appearance of a leak in this area is a matter of time.

What is electrical corrosion and why does it occur?

Electrochemical corrosion of metal leads to the fact that even stainless steel can be destroyed. The main reason for the development of corrosion processes is stray currents in the heated towel rail.

If the metal through which the current flows is exposed to water (our case), then breakdowns occur in it, which become sources of rust.

If the general grounding is properly organized, the problem does not arise

This process is explained quite simply:

1. The occurrence of breakdowns is provoked by potential differences on the metal pipe. With proper design and assembly of communications, the difference rarely arises - all parts must be grounded and connected to the anodic protection of the house. In the case when all the pipes are made of the same material, this is what happens, because where communications have not been changed for a long time, the problem of electrocorrosion is not so relevant.

Plastic pipes break the ground loop, which becomes a source of problems

Metal-plastic inserts (as in this photo) lead to the appearance of a potential difference

1. If there is a potential gap between the riser and the heated towel rail (installation of a polypropylene or metal-plastic insert), the situation gets worse. A potential difference arises, and water in this case acts as an electrolyte.
2. Static electricity poses an additional threat. It accumulates when water rubs against the walls of pipes made of dielectric (polypropylene or polyethylene).

Ground wire

1. In most cases, all processes proceed relatively unnoticed until drops of water appear on the surface of the heated towel rail. After this, the speed of corrosion processes increases significantly, and it becomes almost impossible to stop them.

Where droplets appear, corrosion is inevitable

The most unpleasant thing in this situation is that you may be completely innocent of the appearance of stray currents. But during the renovation, a neighbor can install a heated towel rail from a metal-plastic pipe or mount a plastic adapter between the riser and the dryer. The result will not take long to arrive!

There is another reason - a less conscientious resident of your home may ground an electrical appliance to a metal pipe of the hot water supply system. Such a device is usually either a washing machine or a “bug” for unwinding the meter.

The result is not only the development of corrosion processes, but also an increased risk of receiving a sensitive electric shock when touching the pipe.

Even if all the pipes are metal, additional grounding will not be superfluous

The need for anti-corrosion protection

Protecting metal from influences that have a destructive effect on its surface is one of the main tasks facing those people who work with mechanisms, units and machines, ships and construction processes.

The more actively a device or part is used, the more likely it is to be subject to the destructive effects of atmospheric conditions and liquids that are encountered during operation. Many branches of science and industrial production are working to protect metal from corrosion, but the main methods remain unchanged and consist of creating protective coatings:

• metal;
• non-metallic;
• chemical

Non-metallic coatings are created using organic and inorganic compounds; their operating principle is quite effective and differs from other types of protection. To create non-metallic protection in industrial and construction production, paint and varnish compositions, concrete and bitumen and high-molecular compounds are used, especially actively adopted in recent years, when polymer chemistry has reached great heights.

Chemistry has contributed to the creation of protective coatings using methods:

• oxidation (creating a protective film on metal using oxide films);
• phosphating (phosphate films);
• nitriding (saturation of the steel surface with nitrogen);
• cementation (combination with carbon);
• bluing (compounds with organic substances);
• changing the composition of the metal by introducing anti-corrosion additives into it);
• modification of the surrounding corrosive environment by introducing inhibitors that affect it.

Electrochemical corrosion protection is the reverse process of electrochemical corrosion. Depending on the shift of the metal potential to the positive or negative side, anodic and cathodic protection are distinguished. By connecting a protector or a direct current source to a metal product, cathodic polarization is created on the metal surface, which prevents the destruction of the metal through the anode.

Electrochemical protection methods consist of two options:

• the metal coating is protected by another metal that has a more negative potential (that is, the protecting metal is less stable than the protected one), and this is called an anodic coating;
• the coating is applied from a less active metal, and then it is called cathode.

Anodic corrosion protection is, for example, galvanized iron. Until all the zinc from the protective layer is used up, the iron will be relatively safe.

Cathodic protection is nickel plating or copper plating. In this case, the destruction of the protective layer also leads to the destruction of the layer that it protects. Attaching a protector to protect a metal product is no different from the reaction in other cases. The protector acts as an anode, and what is under its protectorate remains safe, using the conditions created for it.

Formation process

How they are formed The reason for the occurrence of stray currents is a large number of equipment operating from an electric charge, as a result, the following elements are potential sources:

• the presence of chargers in such objects as substations, overhead lines with a neutral conductor, distributors;
• the occurrence of activity as a result of the destruction of the insulating layer of wires carrying current in cables and overhead lines, where the neutral is insulated;
• the presence of a connecting technological link between the conductor and the soil in structures with a grounded neutral and rail vehicles driven by current.

The mechanism of spontaneous discharges can be considered using the example of one of the above points.

One end of the neutral wire is connected to the power station charger, and the other is connected to the PEN bus of the energy consumer, which has a connection to the charger. It follows that the potential difference of the electrical value between the terminals forms stray currents, since the energy will be transferred to the charger, which in turn will form a circuit.

In this case, the volume of losses does not have a large percentage, since it will pass along the path of the least resistance, but a certain part will fall into the ground.

Similarly, energy leakage occurs in the case of damaged wiring insulation.

In this case, there is no constant uninterrupted leakage, since its occurrence is signaled by the system and the area is automatically localized, and according to the standards, there is a certain period of time allotted for troubleshooting.

Currents on the rails When using urban electrified transport, voltage is supplied from the substation to the traction system, which passes to the rails and completes the reverse cycle. If the rails, as an iron base, are not stable enough relative to the conductor, this leads to the formation of stray current locations in the soil, then any metal structure that appears in their path, for example, plumbing products, acts as a conductor.

All this will lead to accelerated destruction of metal products.

What is corrosion

The process of destruction of the top layer of a metal material under the influence of external influences is called corrosion in the broad sense.

The term corrosion in this case is only a characteristic of the fact that a metal surface enters into a chemical reaction and loses its original properties under its influence.

There are 4 main signs by which you can determine that this process exists:

• a process that develops on the surface and eventually penetrates into the metal product;
• the reaction occurs spontaneously because the stability of the thermodynamic balance between the environment and the system of atoms in the alloy or monolith is disrupted;
• chemistry perceives this process not simply as a destruction reaction, but as a reduction and oxidation reaction: when entering into a reaction, some atoms replace others;
• the properties and characteristics of the metal undergo significant changes during such a reaction, or are lost where it occurs.

Closed-loop galvanic cell

Rust coating of steel parts in a humid environment is the most common example of galvanic corrosion. There is no absolutely pure water in nature; it always contains impurities that conduct electricity. This means that ordinary, non-distilled water is always an electrolyte. In real-life iron there are inhomogeneities due to the crystal structure and all kinds of impurities. Because of this, there are zones on the metal surface with different electrochemical potentials. The ingress of moisture onto the surface of ordinary steel causes the formation of a large number of microscopic galvanic elements closed on themselves. Currents flow through them, causing electrochemical corrosion. Their values ​​are negligible, but serious destruction occurs over a long period of time.

More severe electrochemical corrosion occurs when two objects made of different materials are placed in an electrolyte. Then the potential difference between them reaches several volts, and the current value is also very large. In essence, a full-fledged galvanic cell is formed. This type of corrosion occurs in inexpensive plumbing fixtures of unknown origin.

Methods for protecting metal

Electrochemical corrosion is one of the main obstacles encountered in the path of human activity. Protection from the effects of destructive processes and their occurrence on the surfaces of structures and structures is one of the permanent and urgent tasks of any industrial production, and any everyday human activity.

Several methods of such protection have been developed, and all of them are actively used in the daily life cycle:

• Electrochemical protection is an electrolytic operating principle using chemical laws that protects metal using the anodic, cathodic and sacrificial principles.
• Electric spark processing using various installations - non-contact, contact, anodic-mechanical.
• Electric arc spraying is the main advantage in the thickness of the applied layer and the relative cheapness of the process.
• Effective anti-corrosion treatment involves removing contaminants and cleaning the surface being treated, followed by applying first an anti-corrosion layer and then an additional protective layer to the surface.

All these methods have been developed in the process of human activity in order to protect tools, means of transportation and transportation at the junction of several industrial sectors, and using scientific achievements.

Electrochemical corrosion, which is a natural process of destruction of a metal surface under the influence of neutral or aggressive environmental factors, is a complex problem. Machine-building, transport, industrial enterprises and means of transportation suffer losses from it. And this is a problem that requires daily resolution.

Polymer processing - a solution to the problem without grounding

But you can solve the problem in another way by treating the inner surface of a stainless steel water heated towel rail with a special polymer composition. It will create an insulating coating that will “work” effectively, preventing the formation of potential differences and the occurrence of corrosion.

Polymer treatment of water heated towel rails is an additional service that is performed by our company at the buyer’s request. And you can order it online on the ZIGZAG website.

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Types of corrosion

Depending on the type of metal and the redox reaction occurring with it, corrosion can be:

• uniform or uneven;
• local and point (individual areas for some reason reacted, while others did not);
• ulcerative, also known as pitting;
• subsurface;
• cracking;
• intercrystalline, occurring along the boundaries of a metal crystal.

Also, depending on what external factors affect the surface, corrosion can be chemical or electrochemical. Chemical corrosion occurs as a result of certain reactions under the influence of chemical interactions, but without the participation of electric current, and can even be inherent in oil and gas. Electrochemical is distinguished by certain processes; it is more complex than chemical.

On video: metal corrosion.

Why haven’t similar difficulties arisen before?

Strange as it may sound, progress has become the reason for the emergence of such a problem as potential difference in engineering systems. Namely, the widespread replacement of metal pipes with plastic ones. As long as the hot water supply, hot water supply and heating pipelines were completely metal, no difficulties arose. And there was no need to separately ground each radiator, faucet or heated towel rail either - all pipes were grounded centrally in the basement of the house, in two places. And all metal appliances in bathrooms and toilets automatically became safe and protected from stray currents.

We advise you to study Electrical Safety Group 2

The transition to plastic changed everything: on the one hand, pipelines began to last longer, and on the other hand, there was a need for additional protection of plumbing equipment. And here it’s not only about the pipes themselves, because in terms of conductivity, metal-plastic is close to traditional metal, but also about the fittings - connecting elements. More precisely, in the materials from which they are made and which cannot provide electrical contact with the aluminum “core” of the metal-plastic pipe.

Measurement methods

When laying a pipeline, stray currents are calculated by measuring the potential difference between two points on the earth's surface, perpendicular to each other and located at an equal distance of 100 m. Measurements are made every kilometer.

Measuring instruments must have an accuracy class of at least 1.5 and an intrinsic resistance of 1 MOhm. The potential difference between the measuring electrodes should not exceed 10 mV. In terms of time, one measurement should last at least 10 minutes, with the result recorded every 10 s.

Measurements in the area of ​​operation of electric transport should be carried out during peak load. If the potential difference exceeds 0.04V, then this is a sign of the presence of stray currents.

A pair of reference electrodes can be used as measuring instruments: copper-sulfate portable and connecting. In addition, you will need a digital multimeter to take measurements, as well as a flexible insulated wire, the length of which must be at least 100 meters.

Despite its small significance, this phenomenon can cause significant damage to underground (and other) communications. The sources of stray currents can be very different. Therefore, it is necessary to take all preventive measures to eliminate this undesirable effect.

Finally, we recommend watching a useful video that clearly shows how to protect yourself from this phenomenon:

So we looked at the causes of stray currents and protection against them. Now you know what it is and how to get rid of this phenomenon even at home!

You probably don't know:

1. Essence of the method

The essence of the method is to measure the potential difference along the route of the designed structure between two points on the ground every 1000 m in two mutually perpendicular directions with the measuring electrodes separated by 100 m to detect stray currents.

Voltmeters with an internal resistance of at least 20 kOhm per 1 V scale with measurement limits: 0.5-0-0.5 V; 1.0-0-1.0 V; 5.0-0-5.0 V or other close to the specified limits. Copper sulfate reference electrodes.

(Changed edition, Amendment No. 1).

3. Taking measurements

The measuring electrodes are placed parallel to the future route of the structure, and then perpendicular to the axis of the route.

Voltmeter readings are taken every 5-10 s for 10-15 minutes at each point.

If the largest swing of the potential difference (the absolute potential difference between the largest and smallest values) exceeds 0.50 V, this indicates the presence of stray currents.

(Changed edition, Amendment No. 1).

APPENDIX 5 Recommended

System clogging and mechanical defects as the cause of a non-functioning heated towel rail

A water towel dryer is often unable to heat up precisely due to mechanical faults. Shut-off valves often fail. Even high-quality ball valves break and crack over time. Such a faucet must be replaced by calling a specialist, since it will not be possible to do it quickly and efficiently on your own.

Another reason is clogging of the entire DHW system. This often happens in houses with poor quality water, which contains a lot of impurities and metal salts. Build-ups and contaminants appear in the pipes, reducing water pressure. In this case, the simplest solution to the problem of a cold heated towel rail would be to clean the entire system, since replacing a component is a labor-intensive and costly process. Special chemicals are poured into the heated towel rail. After a while, the substance is drained from the device, and the pipe walls are cleaned with a metal brush or wire. Do not forget that for all these procedures you will have to turn off the common house riser.

To solve this unpleasant situation, we introduced into our production a technology for protecting metal from stray currents - POLYMER+

The inner wall of the stainless pipe is covered with a polymer film, thereby eliminating contact of the coolant with the metal. This material does not conduct electricity, so it is an excellent insulator. Moreover, the polymer is non-toxic, harmless to humans and the environment, resistant to high temperatures and durable.